Torque control device for differential speed scroll centrifuge



J1me 1955 L. F. HESSION ETAL TORQUE CONTROL DEVICE FOR DIFFERENTIAL SPEED SCROLL CENTRIFUGE Filed Feb. 13. 1964 Invento s A Ema Finuus [Mas/av 0' "(L06 BRAOLEX mad- M Attorney;-

United States Patent 3,191,444 TORQUE CONTROL DEVHIE FGR DIFFERENTIAL SlEED SCROLL CENTRIFUGE Laurence Francis Hession and Douglas Bradley, Camberley, England, assignors to Pennsalt Chemicals Corporatiou, Philadelphia, Pa, a corporation of Pennsylvania Filed Feb. 13, 196i, Ser. No. 344,7il6

Claims. (Cl. 74-2) This invention relates to centrifuges. More specifically this invention relates to torque control devices for centrifuges of the differential-speed scroll type (e.g. worm centrifuges) Still more specifically this invention relates to centrifuges of the general type as shown in US. Patent 2,703,- 676.

The invention will be better understood from reference to the attached drawings in which:

FIGURE 1 is a schematic side view of a centrifuge embodying the invention and shown for environmental purposes;

FIGURE 2 is an enlarged fragmentary sectional view taken on line 22 of FIGURE 3, with parts shown in section. A tripped position of the apparatus is shown in phantom lines; and

FIGURE '3 is a sectional view taken on the line 33 of FIGURE 2.

The centrifuge as shown schematically in FIGURE 1 is of the type in which solid material collects on the walls of the centrifuge bowl A andis directed towards an outlet B at one end by the action of a scroll C which is coaxial with, but rot-ates at -a different speed from, the centrifuge bowl. This difference in speed is brought about by having a common drive D for the scroll and the centrifuge and including differential gearing E between the drive on the one hand and the scroll and centrifuge bowl on the other. The difference in speed can be varied according to the ratio of the differential gearing. Centrifuges of this type are herein referred to as centrifuges of the type described.

In order to minimize the risk of damage should the centrifuge and scroll become jammed together either by excess solid material or by, for example, a stray bolt in the solid material, a torque arm 1 is connected at one end to the pinion shaft F of the differential gearing and engages at its free end a spring loaded lever tripping mechanism G, such that when a predetermined torque has developed the torque arm trips and thus allows the pinion shaft to rotate freely, so that no further relative rotation between the scroll and the centrifuge bowl occurs. As used herein, the term differential gearing mechanism refers to the differential gearing, the torque arm and the spring loaded lever tripping mechanism- However, due to vibrations set up in the spring by rapid fluctuations in the torque and possibly also due to a time lag between movement of the torque arm and the compression or expansion of the spring the torque arm often vibrates against the lever mechanism, with resultant jarring and damage both to the lever mechanisms and to the gears. A simple spring loaded lever tripping mechanism consists of a bell crank and a spring pivoted about fixed positions with respect to each other, the free end of the spring being connected to one arm of the bell crank while the other is urged by the spring towards the torque arm to engage against it.

According to one aspect of the invention, a differential gearing mechanism for a centrifuge of the type described includes (a pneumatic or hydraulic cushion between the spring and the torque arm. As a result of the invention,

the working life of the components of the differential gearing mechanism is considerably lengthened and the efiiciency of the centrifuge to which it is fitted is increased,

3,191,444 Patented June 29, 1965 I a a centrifuge apparatus comprising a centrifuge and the novel differential gearing mechanism comprising a second aspect of the invention. We find that this pneumatic or hydraulic cushion may conveniently operate between the torque arm and the lever mechanism.

The cushion may conveniently be provided by a piston which operates against fluid pressure in a cylinder. Preferably the end of the piston rod is urged against the free end of the torque arm and the spring loaded lever tripping mechanism is connected to the cylinder. The alternative of connecting the spring loaded lever tripping mechanism to the piston rod with the torque arm engaging with the cylinder is also possible.

When the fluid pressure is gas pressure, that is to say there is a pneumatic cushion, the cylinder is preferably connected to a continuous supply of gas under pressure and in this case the connection must be a flexible tube so as to permit movement of the cylinder should tripping occur An expansion chamber may be provided between the cylinder and the supply. The gas we generally use is, for convenience, air. The pressure required within the cylinder will vary accord-ing to the process application on which the centrifuge is being used. Alternatively the cylinder may be pumped up and then sealed off from the supply, and in this case it may have to have an expansion chamber.

When the fluid pressure is liquid pressure, that is to say there is a hydraulic cushion, the cylinder will contain a liquid, for example, oil, and will have an expansion chamber into which the liquid is forced during compression by the piston. For instance a bleed valve may lead to a. chamber consisting of bellows which act either against a spring or against pneumatic or hydraulic pressure urging them towards the piston.

A pressur gauge may be fitted to indicate the pressure in the cushion in pounds thrust. For example, if a pneumatic cushion is provided by a piston operating in a cylinder connected by a pipe to a continuous gas supply, the gauge may be included in this pipe. It is very advantageous to include such a gauge as it is then possible to operate at high values of torque close to the value at which tripping occurs without the disadvantage of not knowing when tripping is about to occur. In practice, therefore, it is possible to use the centrifuge more efiiciently. A similar advantage may be had by using a pressure switch in the gas supply pipe, this switch being set to a slightly lower value than the value at which tripping occurs so that it gives a warning just before tripping could occur. It may be connected to the centrifuge drive or feed so as to cut this out before tripping can occur.

The accompanying drawing in FIGURES 2 and 3 illus trates a part of a differential gearing mechanism according to the invention. A torque arm 1 is secured at its Wide end to the pinion shaft -'F of differential gearing which is connected to a centrifuge of the type described. A torque lever 2 is secured to an axle 3 which is mounted in a fixed position and comprises one arm of a bell crank, the other arm being the arm '4 whose free end is connected to one end of a spring housing 5, the other end of the spring housing being secured to an axle 6 which is mounted in a fixed position. This spring housing consists of two parts, 8 and 9, one slidable within the other and urged apart by a spring 10. In conventional differential gear-ing mechanisms the torque lever 2 engages against a torque arm 1 direct, so that on rotation of the torque arm in an anti-clockwise direction the bell crank rotates on the axle 3 in a clockwise direction and compresses the spring 10. As soon as the arm 4 has rotated to such an extent that it and the spring housing 5 are in a straight line, the lever mechanism is in the tripping position; that is to say, as soon as the arm 4 is caused to rotate any further by movement of the torque arm 1, the torque lever springs free (up in an overrcenter action (to the phantom line position in [FIGURE 2, for instance) from the torque arm 'which then rotates freely on the pinion shaft, This results in disengagement of the gearing so that there is no further relative rotation between the scroll and centrifuge. The torque which has to be applied before this tripping posi- Ition is reached may be selected by adjustment of a nut 11 which is integral with the part 9 and is screwed onto a shaft passing through the spring housing 5.

- In the differential gearing mechanism according to the invention which is illustrated, a plunger 12 is urged against the torque arm 1 by a piston operated by pneumatic pres- .sure in a cylinder 13, and the torque lever 2 is secured to .the cylinder at 14. A supply of air under pressure is provided to the cylinder by flexible tubing of braided nylon, 15, linked through a gauge cock isolating valve 16 to a main air supply pipe 17. Included in this main pipe between the source of air and the valve 16 are a master pressure gauge 18, a non-return valve 19 to prevent tripping should the supply of air fail, and air pressure regulator 20. The pipe "17 may supply air to similar differential gearing mechanisms attached to other centrifuges.

The tube may, of course, be of any suitable flexible material. i

There may be a stop for engagement by the top surface of the arm 4 to prevent the spring urging the bell crank to rotate in an anti-clockwise direction to an undesirable extent when the torque lever swings in a clockwise direction.

The air is conveniently supplied at a maximum pressure of 150 pounds per square inch, from, for example, the users piped compressed air supply, .or from a cylinder which may be pumped up to operating pressure either manually or by the users compressed air supply.

It should be understood that variations are-possible within the scope of the invention. Therefore, having particularly described our invention, it is to be understood that this is by way of illustration, and that changes, omissions, additions, substitutions, and/ or other modifications may be made without'departing from the spirit of the invention; Accordingly, it is intended that the patent shall cover, by. suitable expression in the claims, the various features of patentable novelty that reside in the invention.

We claim:

1 In a centrifuge comprising a hollow bowl, a scroll inside the bowl for discharging solids from said bowl, means for driving the bowl, differential gearing means rotatably linking the bowl and scroll, a torque control mechanism, the gearing means having a pinion, said mechanisni including a torque arm attached and extending radiallyffronr the shaft oi said pinion and overload tripping means opposing and normally blocking the rotation of said torque arm, said overload tripping means comprising a torque lever, a torque axle free to pivot about a fixed axis and fixedly mounting one end of said torque lever, a bell arm mounted on the torque axle spaced from said d torque lever, a compression spring assembly having one end secured to a fixed pivot point and the other end pivotally secured to a movable pivot point on the distal end of said bell arm, the movable pivot point being normally disposed on one side of an imaginary line drawn between the torque axle and the fixed pivot point whereby the compression spring assembly imparts a biasing force to said torque lever causing the torque lever to oppose rotation of the torque arm and whereby an excessive force from the torque arm in opposition to the torque lever the compression spring assembly will yield to permit the movable pivot to trip to the other side of the imaginary line so that the torque lever is thereby moved out of the path of the torque arm and the latter is permitted to rotate freely, the improvement including fluid motor means having a cylinder and movable plunger, the distal end of said torque lever mounting said cylinder, the plunger yieldingly engaging the torque arm of said mechanism when said movable pivot point is on the said one side of said line, and means supplying fluid pressure to said fluid motor means.

2. A centrifuge as described in claim 1 wherein the means supplying fluid pressure to said fluid mot-or means includes indicator means indicating the fluid pressure supplied, .and means for regulating the fluid pressure.

*3. A centrifuge as described in claim 1 wherein the means supplying fluid pressure to said fluid motor means includes an expansion chamber biased toward a restricted volume.

4. A centrifuge as described in claim 1 wherein means are provided to adjust the compression on the compression spring assembly.

' 5. In a centrifuge comprising a hollow bowl, a scroll inside the bowl for discharging solids 'from said bowl, means for driving the bowl, diiferential gearing means rotatably linking the bowl and scroll, a torque control mechanism, the. gearing means having a pinion, said mechanism including a torque arm attached and extending ra dially from the shaft of said pinion and overload tripping means opposing and normally blocking the rotation of said torque arm, said overload tripping means comprising a torque lever, overrcenter .spr-ing biased means causing the torque lever to oppose rotation of the torque arm and (whereby upon an excessive force from the torque arm in opposition to the torque lever the over-center means will yield and go over center so that the torque lever is thereby moved out of the path of the torque arm and the latter is permitted to rotate freely, the improvement including fluid motor means having a cylinder and movable plunger, the distal end of said torque lever mounting said cylinder, the plunger yieldingly engaging the torque arm of said mechanism, and means supplying fluid pressure to said fluid-motor means.

No references cited.

DON WAITE, Primary Examiner. 

1. IN A CENTRIFUGE COMPRISING A HOLLOW BOWL, A SCROLL INSIDE THE BOWL FOR DISCHARGING SOLIDS FROM SAID BOWL, MEANS FOR DRIVING THE BOWL, DIFFERENTIAL GEARING MEANS ROTATABLY LINKING THE BOWL AND SCROLL, A TORQUE CONTROL MECHANISM, THE GEARING MEANS HAVING A PINION, SAID MECHANISM INCLUDING A TORQUE ARM ATTACHED AND EXTENDING RADIALLY FROM THE SHAFT OF SAID PINION AND OVERLOAD TRIPPING MEANS OPPOSING AND NORMALLY BLOCKING THE ROTATION OF SAID TORQUE ARM, SAID OVERLOAD TRIPPING MEANS COMPRISING A TORQUE LEVER, A TORQUE AXLE FREE TO PIVOT ABOUT A FIXED AXIS AND FIXEDLY MOUNTING ONE END OF SAID TORQUE LEVER, A BELL ARM MOUNTED ON THE TORQUE AXLE SPACED FROM SAID TORQUE LEVER, A COMPRESSION SPRING ASSEMBLY HAVING ONE END SECURED TO A FIXEDLY PIVOT POINT AND THE OTHER END PIVOTALLY SECURED TO A MOVABLE PIVOT POINT ON THE DISTAL END OF SAID BELL ARM, THE MOVABLE PIVOT POINT BEING NORMALLY DISPOSED ON ONE SIDE OF AN IMAGINARY LINE DRAWN BETWEEN THE TORQUE AXLE AND THE FIXED PIVOT POINT WHEREBY THE COMPRESSION SPRING ASSEMBLY IMPARTS A BIASING FORCE TO SAID TORQUE LEVER CAUSING THE TORQUE LEVER TO OPPOSE ROTATION OF THE TORQUE ARM AND WHEREBY AN EXCESSIVE FORCE FROM THE TORQUE ARM IN OPPOSITION TO THE TORQUE LEVER THE COMPRESSION SPRING ASSEMBLY WILL YIELD TO PERMIT THE MOVABLE PIVOT TO TRIP TO THE OTHER SIDE OF THE IMAGINARY LINE SO THAT THE TORQUE LEVER IS THEREBY MOVED OUT OF THE PATH OF THE TORQUE ARM AND THE LATTER IS PERMITTED TO ROTATE FREELY, THE IMPROVEMENT INCLUDING FLUID MOTOR MEANS HAVING A CYLINDER AND MOVABLE PLUNGER, THE DISTAL END OF SAID TORQUE LEVER MOUNTING SAID CYLINDER, THE PLUNGER YIELDINGLY ENGAGING THE TORQUE ARM OF SAID MECHANISM WHEN SAID MOVABE PIVOT POINT IS ON THE SAID ONE SIDE OF SAID LINE, AND MEANS SUPPLYING FLUID PRESSURE TO SAID FLUID MOTOR MEANS. 